first you need to solve both inequalities system
p+m<= 20
so p<= 20 - m
substitute p<= 20 - m into 5p+ 10m< = 120
5p+ 10m< = 120
5(20-m)+ 10m< = 120
100 - 5m + 10m <= 120
5m <= 20
m<= 4
p<= 20 - m
p<= 20 -4
p<= 16
now you can find variable and non-variable solutions (p,m)
variable:
(15,3)
(10,-5)
Non-variable:
(0,10)
(20,1)
(5,5)
(0,15)
